## anonymous 3 years ago Find the area of an equilateral triangle with side of length 18. (Round your answer to one decimal place.)

1. anonymous

Area= 1/2 base x height tan(60)=h/18 h=18tan(60) right?

2. anonymous

should i be using law of sines

3. anonymous

why use law of sines?

4. anonymous

wait...by law of sines do you mean $\frac{a}{\sin A} = \frac b{\sin B} = \frac c{\sin C}$

5. anonymous

yes, i have three angles (60) and three sides) so the how would i then find the height

6. anonymous

use pythagorean theorem...you have equilateral triangle |dw:1352707222314:dw|

7. anonymous

so the height would cut your triangle into two equal parts..|dw:1352707262694:dw| can you see how to get the height now?

8. anonymous

15.6?

9. anonymous

yes

10. anonymous

11. anonymous

A=(1/2)(18)15.6)

12. anonymous

yes

13. anonymous

by the way.. you can also use your solution a while ago... 18tan (60) you don't need law of sines...just use a calculator for that

14. anonymous

140.4units squared

15. anonymous

yes

16. anonymous

and that solution from earlier would then give me the height?

17. anonymous

hmm wait...something's wrong with it...let me find it first

18. anonymous

should it be 9 instead of 18

19. anonymous

yes it should be 9